Area Forecast Discussion
Issued by NWS Hastings, NE
Issued by NWS Hastings, NE
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
023 FXUS63 KGID 291800 AFDGID Area Forecast Discussion National Weather Service Hastings NE 100 PM CDT Wed May 29 2024 .KEY MESSAGES... - A warm front will push through the area today and provide for slightly higher temperatures/humidity and breezy SE winds, but not much for precipitation chances (20% or less). - Higher shower and thunderstorm chances arrive late tonight (30-60%), then become likely Thursday into Thursday night (60-80%) with the arrival of a weak cold front. - Friday should trend drier through the day, but off and on shower and thunderstorm chances persist each day through the weekend - mainly during the evening/night hours. - Severe weather potential next several days is low by late May standards, but not zero, so would expect periodic at least marginally severe weather. Locally heavy rain will also be possible, but confidence on details (amounts/location) is low. - Ensembles have trended cooler for next week thanks to deeper troughing over the Great Lakes. This implies periodic cold fronts/precipitation chances continuing into next week. && .DISCUSSION... Issued at 450 AM CDT Wed May 29 2024 Today - Tonight: AM surface analysis reveals a stationary front situated from the Neb. Panhandle SEward towards the KC Metro with T/Tds in the 50s/40s N of the boundary, and 60s/50s to the S. There hasn`t been a whole lot in terms of elevated convection early this morning, and latest HRRR/RAP trends don`t offer much potential for our area through the daytime hrs, despite the frontal zone transitioning northward as a warm front. Instead, expect mainly dry conditions and both air temperatures and dew points slightly higher than yesterday on breezy SE winds gusting 25-30 MPH. No significant changes to the forecast thoughts for tonight as scattered convection is still forecast to develop within a broad N-S zone along the Front Range/High Plains this afternoon, then gradually shift E this eve/night. Think the brunt of our potential will come after midnight and on a weakening and sub- severe basis owing to lackluster instability and deep layer wind shear. This general scenario is depicted well in recent 06Z runs of the HRRR/NAMNest. Thursday - Friday: Remnant isolated-scattered showers/weak storms will remain possible (40-60% chance) through Thursday AM, perhaps aided by combination of veering low level jet and embedded MCV(s). A cold front is forecast to enter far N/W portions of the forecast area, generally Ord to Lexington, by the late afternoon hrs. Assuming we clear out for a few hrs around midday, should have a narrow zone of at moderate instability, weak capping, and convergence along to boundary to generate new scattered storms 20-23Z. Exactly how robust this activity is will depend on how much clearing we see during the afternoon, as well as lingering subsidence from a potential departing MCV. If the moderate instability materializes (aided by gradually moistening boundary layer), then strong to marginally severe storms would be possible given effective shear values of 30-35kt. Highest chances for severe (relatively speaking) could favor areas W through S of the Tri-Cities per 03Z SREF calibrated severe probs, but the entire area is outlooked in a Marginal Risk (level 1 of 5) per SPC Day 2 outlook. Large hail and locally severe wind gusts would be main threats, but will need to watch for potential outflow boundary from AM activity to possibly return N and intersect cold front. This would also pose an isolated tornado threat. Convection could continue on at least an iso-scat basis into the overnight, though exact evolution and coverage remains uncertain due to vastly varies solutions regarding strength/placement of LLJ. Some guidance has almost no LLJ, whereas others have 40-45kt Srly flow overriding the gradually southward sinking cold front/outflow. Personally, I think upscale growth for at least north central KS is quite plausible given the general synoptic pattern and increasing instability to the S. Low end PoPs continue into Friday, though to be honest, I`m not seeing a lot for sfc/upper support. Sfc boundary should also be well S of the area by the aftn/eve hrs. It`s only a weak front, though, and expect highs will make it to at least low to mid 70s. Weekend: Models are in general agreement in primarily zonal upper flow for the weekend, but disagree with timing, placement, and magnitude of several embedded shortwaves. In the absence of a coherent/apparent frontal zone, am inclined to think that our chances will tend to be highest during the mid to late evening into the overnight from convection that develops over the High Plains in moist SErly upslope flow, then shifts E/SE. For Saturday night, nearby mid level thermal gradient (H7 temps ranging from 6-8C Neb zones to 10-11C just SW of the area per 00Z EC) and likely increasing LLJ would suggest a favorable pattern for a NW to SE moving nocturnal MCS, somewhere over NE and/or KS. There would probably be some risk of large hail transitioning to damaging wind with any MCS, though due to the nebulous sfc forcing and model differences, the predictability of such evolution/detail is too low this far out. Instability will increase on Sun with continued Srly flow, but so will mid- level temperatures and capping. Some guidance suggests a repeat scenario of Saturday, which seems plausible given potential arrival of next cold front. However, with the higher mid level temperatures would probably need a sufficiently strong and well- timed shortwave, too. IF convection develops, then severe would be possible given strong instability and area residing within southern fringes of W to E belt of 40-50kt effective shear. LLJ could also help sustain activity into Sunday night. The next several days carries a lot of "IFs" and "possible", but IF the repeated rounds of convection come to fruition, then locally heavy rain and flooding could be an issue, as well. 00Z EPS places periodic bouts of PWATs 125-150% of normal over the area Thu through the weekend, and 90th percentile QPF is near 3", in spots, which could go up if member agreement increases. Next Week: Looks like more of the same off and on precip chances continue into early next week before a potentially stronger shortwave swings through Tuesday-ish. Ensemble guidance is quite varied with the amplitude of this shortwave - which then impacts the potential for a more notable longwave pattern shift towards Great Lakes troughing and western CONUS ridging. EPS favors a deeper shortwave on Day 7, and has trended W w/ deeper Great Lakes trough and stronger NW flow for second half of next week. This would cut back on the potential for 90s due to periodic cold fronts/precipitation chances in active NW upper flow. GEFS is weaker/flatter - but even still, it is not quite as warm/dry as runs a few days ago. Just some trends to keep an eye on. && .AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 1241 PM CDT Wed May 29 2024 FEW-SCT mid and high level clouds will move over the area this afternoon. This evening, SCT-BKN mid level clouds will build over the area. Overnight, showers from a decaying line of storms moves in from the west, and skies will begin to lower to MVFR criteria before sunrise on Thursday. There is some uncertainty on how low ceilings will lower, so kept ceilings limited to 020. Scattered to isolated showers will be possible after midnight and continue into Thursday morning. VCSH was maintained due to low confidence in coverage, duration and strength of any precipitation. Breezy SE winds will continue throughout the TAF period with gusts over 20KTs. && .GID WATCHES/WARNINGS/ADVISORIES... NE...None. KS...None. && $$ DISCUSSION...Thies AVIATION...Davis